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(No Model.) 2 Sheets-Sheet 1.

E. POPE. TELEPHONE EXCHANGE SYSTEM.

Patented Mar. 6,1894.

WITNESSES:

INVENTOI? Edwin Papa nil NATIONAL umacuurnma camunv wAsl-uu (No Mariel.)2 SheetsSheet 2.

E. POPEL' TELEPHONE BXGHANGE SYSTEM.

No. 515,939. v Patented Mar. 6,1894;

INVENTOB WITNESSES:

Edwirz- Pope m rumoew. umoeupmmz ucmurw. wmna-ron. :4 e..

' NrrED; STATES ATENT EDWIN POPE, OF QUEBEC, CANADA.

TELEPHON E-EXCHANG E SYSTEM.

SPECIFICATION forming part of Letters Patent No. 515,939, dated March 6,1894.

Application filed August a, 1392. Serial No.442 ,011. on model.)

T0 on whom it may concern:

Be it known that I, EDWIN POPE, a subject of the Queen of Great Britain,residing at Quebec, in the Province of Quebec, Canada, have inventedcertain new and useful Improvements in TelephoneExchange Systems, ofwhich the following is a full, clear, and exact description.

This invention relates to telephone exchange systems, and has specialreference to the construction and operation of multiple switchboards formetallic circuit systems, the objects being to simplify the constructionand thereby lessen the cost, and to simplify the operation of connectingtogether subscribers.

The invention entirely dispenses with the use of spring jacks, andsubstitutes therefor plain contact points in the circuit.

The invention will be described in detail with reference to theaccompanying drawings, in which Figure 1, represents, diagrammatically,the apparatus and circuits of two subscribers, together with a switchingapparatus by means of which communication between subscribers may beestablished. Fig. 2, illustrates the circuits of a numberof subscribersin connection with atest-wire and switch. Figs. 3,and 4, illustrate thecondition of a subscribers circuit when busy and free, respectively.Figs.

5, 6, and 7 represent various circuitsestablished by the operation ofconnecting subscribers together. Fig. 8 is a sectional detail of theswitchboard. Fig. 9, is a sectional detail of the plug connected withthe switching apparatus. Fig. 10, illustrates a modification in theconnections, and Fig. 11, shows how theinventiou may be applied tosingle or grounded circuit systems.

Referring to the drawings by letters and figures, A .I and A K arerespectively two subscribers stations, the two wires leading from eachof which are represented respectively by a, j, and a, j. These wiresextend respectively to corresponding drop magnets and connect the cellsB and B of said magnets in parallel. From the two coils the wires leadto open plugging in points J. J. or K. K., &c., located, one pair oneach section of the multiple board. The wires extending through theswitchboard are represented by A A The point A on the wire j, and thepoint A on the wire a, are connected by a branch conductor 06'. Thisconductor includes a circuit breaker consisting of two contact springs Gand H, which when the drop E is up are electrically connected together.A closed circuit including the subscriber and coil B is therebyestablished, leaving the coil B" in open circuit.

C is the armature of the drop magnet, and C is a bell crank leverpivoted at c, and carrying at its forward end a dog 0 which engages withthree stops, F, F, F, respectively, carried by the drop E; these stopsdetermine the various positions which the drop may take. The third stopF is made wider than the others, so that it will engage with the detentS, arranged alongside of the dog 0 and in such a position that F willstrike S before it strikes 0 For convenience we will assume that thedrops of the two magnets are located on sections J and K, respectively,of a multi ple switchboard, and it is to be understood that the dropmagnets are constructed and connected up alike, and that the drop E ofeach one is in constant communication by wires 6, with a test wire'T.Each of the switchboard operators is provided with a number of switchingdevices N, say a dozen, the number being sufficient to make all theconnections required at any one time. This switch consists preferably ofa cylinder at of insulating material, having located in its surface four longitudinal rows of metallic contact pieces. The positions of thecontacts of each row are shown in Fig. 1, and indicatedby 1st, 2nd, 3rd,4th. Upon the cylinder eight metallic springs 1, 12, 2, 3, 3,4 and 5, 5,bear. A crank it is used to rotate the cylinder from one position toanother to bring the rows of contacts beneath the springs, and a spring11 bearing upon the periphery of a notched wheel insures the accuracy ofmovement of the cylinder. The wheel has eight notches allowing thecylinder to turn eight times in a revolution, and making one fullconnection in a half revolution. The springs 1, 12, are connectedthrough a flexible cord with two contacts carried by a plug 11, andsprings 2, 12, connect with another plug 2:2, through a flexible cord inthe same manner; the springs 3, 3, connect with the operatorsinstruments; spring 4 with the test battery T and test wire, and springs5, 5, with the magneto current used for calling.

The construction of the plugs 11 and 22 is shown in detail in Fig. 9,wherein it will be seen to consist of a block of insulating material m,carrying a cup-shaped metallic socket m, anda metallic spring minsulated from the socket. The socket and spring are respectivelyconnected with the wires of the flexible cord leading to the springs onthe switch, as described. The face of the switchboard is preferablyaslab of slate, marble or other fireproof material forming a goodinsulator through which are passed bolts or pins 0, p, with a shoulderin front and fastened with a nut in the back. (See Fig. 8.) These arearranged in pairs, one of each pair adapted to fit the socket m, and theother to make contact with the spring m when the plug is adjusted.

The operation of the system is as follows: The normal or free conditionof the apparatus is shown in Fig. 1. When subscriber A J calls, thecurrent which he sends over line passes through coil B, and circuitbreaker G H E. O is attracted and drop E fall. But as the circuit isopened between G and Himmediately, B becomes de-energized, and 0 engageswith the stop F. Operator at board noting which subscriber has called,puts plug 11 of one of the switches N into the subscribers line at thepoints J J. Now the springs of the switch are supposed to be in thefirst position upon the cylinder; consequently when 11 is plugged into JJ, the operators telephone 0, P, is put into circuit with the callingsubscriber. This circuit is traced as follows: from operators telephoneto spring 3, through the switch to spring 12, wire A wire a, subscriberA J, wire j, wire A flexible cord and spring 1, through the switch tospring 3, and back to telephone. Operator gets the number of connectionwanted then puts plug 22 into K K which represents the subscriberwanted. It the line is free a click is heard in the telephone, which iscaused by the testing battery T, acting through the following circuit:from battery T, to spring 4, through the switch to spring 3, operatorstelephone, second spring 3, through the switch to spring 2, wire A fromK board, contact G, drop E, wire e, test wire T, wire t and back to testbattery. when this circuit is established the current is free to takeeither of two paths one of which is the one just traced, and the otheris through the spring 12, wire A and coil B, of the drop magnet, but asthe current takes the path of lowest resistance, very little of it willflow through the magnet and the drop will remain up. If subscriber A Khad been busy, his drop E would have been down and the connection G H Ebroken, consequently the calling operator would have gotten silence,instead of the click when she plugged into K K. Silence or a click istherefore the indication of a busy or free line. If the line is free theoperator turns the switch N to the second position which puts themagneto cnrrent into the called subscribers line by the followingcircuit: from magneto to spring 5, through the switch to spring 12, cordand wire A coil B, wire j subscriber A K, wire ct, 0011 B, wire A spring2, through the switch to spring 5 and back to the magneto instrument. Asthis current passes through E and B at K, drop E falls, and as thiscircuit is not affected by G H, it remains closed. Operator at J thenmoves the switch to the third'position which connects the two linestogether with her telephone in circuit, as folows: from operatorstelephone to spring 3, through the switch to spring 1, cord and wire Awire j, subscriber A J, Wire a, wire A spring 1 2, cord and wire A fromboard K, wire j subscriber A K, wire a, wire A spring 2, through theswitch to spring 3, to operators telephone. Then finding the connectionproperly made operator puts the switch to the fourth position, whichleaves the two subscribers together with the centralinstrument out, asfollows: from subscriber A J by wire a,wireA spring12, wire A from Kboard, wire j, subscriber A K, wire a, wire A to spring 2, throughswitch to spring 1, wire A wire 3 and back to subscriber A J. XVhensubscriber rings off, E at board 5 drops until F strikes S, and theoperator sees by the position of the plugs that it is a ring 0% andtherefore restores E to its first position, takes out plugs and movesthe switch to the next position, which is its first. When the operatorcalls up a subscriber whose annunciator is at another board the magnetocurrent acting continuously on the magnet at that board allows the dropto fall until it strikes S, which is its third position. When the callis completed which is determined by the armature coming to rest, theoperator at that board presses the outer end of the stop S, and allowsthe stop F to escape and engage with 0 at the fourth position. Then whenthe subscriber rings 01f, E drops to its lowest position and theoperator restores it to first position.

Fig. 2 shows the connections when the switch is in first position, andplug 11 placed to answer a call from A J with central instrument incircuit. If subscriber K is the connection wanted, operator puts plug 22to that wire, but the connection G H E being broken the local batteryand test wire do not act, and the telephone is silent, indicating thatthe line is engaged, see Fig. 3. If another, K is wanted, plug 22 is putto that wire, and G H E being connected the test bat- E ery actsindicating that the line is free, see

Fig. 5 shows the connections when the switch is in its second positionwith the calling current on K.

Fig. 6 shows the connections when the switch is in its third positionwith A J and K connected and central instruments in,

Fig. 7 is the fourth position of the switch, showing the two subscribersconnected straight and central out.

In Fig. 10 a modification of the connections is shown wherein the twocoils of the drop magnet are connected in series on the subscriberscircuits, but the connections G H E- are so arranged as to produce thesame results. The test wire here leads to a third spring upon drop Ealso.

Fig. 11 shows how my invention may be used on single Wire or groundedcircuits. The subscribers wire leads directly through the coils of thedrop magnet and thence through the switchboard as before, a branch leadsfrom the line between coils to ground through drop E. Line '1 is thetest which terminates in a spring against drop E. The operation is thesame as for metallic circuits. Putting double plug into A T gives eithera click or silence. 7

Having described my invention, I claim- 1. In a telephone exchangesystem, a drop magnet having two coils, one in a normally closed circuitwith the subscriber and the other in a normally open circuit, incombination with a circuit breaker controlled by the drop andconnections whereby the circuit breaker will put the two coils into thesame or separate circuits, substantially as described.

2. In a telephone exchange system, the combination with a subscriberscircuit, of a test battery normally in connection therewith, andmechanism controlled by the subscribers drop for breaking the,connection with the test battery, for the purpose set forth.

3. In a telephone exchange system, an annunciator and armature having adrop provided with a plurality of stops to limit its movement, incombination with a circuit breaker operated by the drop, and controllingthe circuit of the drop magnet.

4. In a telephone exchange system, a drop magnet having its coilsconnected respectively in the two wires of a subscribers circuit, incombination with a normally closed branch circuit, putting one of saidcoils in a closed circuit with the subscriber, the subscribers two wiresbeing otherwise disconnected, and means whereby the drop magnet may opensaid branch circuit, for the purpose set forth.

5. In a telephone exchange system, the combination with a subscriberscircuit, of a test battery normally in connection therewith andmechanism controlled by the subscriber for breaking the connection withthe test battery, for the purpose set forth.

In testimony whereof I subscribe my signature in presence of twowitnesses.

EDWIN POPE.

Witnesses:

W. A. H. CUFF, A. CASAULT.

